Glossary & Acronym List of G0 Terms which drive people crazy.

Initially compiled by Greg Smith: send new ones to me and I'll add 'em here.
Now updated by C. Ellis : send new ones to me and I'll add 'em here.


last update :03/14/2006
The mark FORWARD in the meaning column indicates that this acronyms was mostly relevant in the forward angle configuration.

Term Meaning (my interpretation, anyway)
120 Hzz Oversampling the data. Reading out 4* more often than the helicity is changing.
30 Hz Approximate helicity reversal frequency.
ABU Acceptable Beam in Use.
adiabatic damping Property by which the transverse emittance decreases as the momentum increases. Adiabatic means no net gain or loss of energy. Should mean that position differences get smaller as the beam is accelerated.
Analog Ring Sampler

ASIC Application Specific Integrated Circuit
BCM Beam Current Monitor. Measures absolute beam current.
BCM calibration Determination of pedestals and slopes in plot of BCMs vs the Unser current monitor.
beam feedback Process of feeding back on measured charge asymmetry and position differences in order to minimize those quantities.  The Hall C IA and PZT and the Hall A IA are used to affect these beam characteristics.
bleedthrough Bleedthrough, or leakage, describes how photoinjector laser light from the other halls, even our own Hall C  DC laser light, leaks through our slit and winds up in our tof spectrum. We see 499 MHz components under our whole spectrum from this. Typically around 50 nA, but has a horrendous charge asymmetry associated with it.
BLM Beam Loss Monitor. A BCM or PMT used by MCC to make sure transmission is good.
BPM Beam Position Monitor- a stripline device with x&y pickup plates or wires to measure beam position.
BPM Calibration Find the pedestal values of the 4 wires which combine to give the x & y positions of the beam.
BS See any collaboration member. We're full of it. Sometimes also refers to Beam Studies done by MCC on a quasi-regular basis.
BTA Beam Time Accounting. (beam counting, er, I mean bean counting).
buddy system of comparing detectors on opposite sides in order to determine the dead time.
cable jiggling Done to get rid of error lights on the NA electronics.
Cavity BPM An RF cavity beam position monitor. Temperature controlled, sensitive, but drifts.
CFD Constant Fraction Discriminator
CHL Central Helium Liquifier: supplies 2K liquid helium coolant for the accelerator cavities.
CEBAF Online Data Acquisition
Coil pulsing Periodically done to kick the beam in x&y at the target, in order to map out the detector sensitivity to position differences.
CD Conditioned Direct Counters : yield and asymmetries of each FPD or CED in time with the trigger signal (OR(CED) AND OR(FPD)) and condionned by the Cerenkov trigger.
controlled access Need to get a key & talk to the MCC to get into the hall. In between restricted access and beam permit.
COO Conduct of Operations
cut0 FORWARD: The region in the TOF spectra to the left of (earlier than) the pion peak and to the right of (later than) the elastic peak. We're talking the extreme unphysical edges of the tof spectrum, where all we see is the bleedthrough.
cut1, cut2, cut3 FORWARD:The region in the TOF spectra between the pion peak and the elastic peak is divided into 2 regions: an early region (cut1) next to the pion peak, and a later region next to (but not including) the elastic peak. Cut 3 is at times later than the elastic peak. Cut 1,2,and 3 do not include any of the elastic or pion peaks, they are background cuts.
CUE Common User Environment: the JLab computing group's term for our JLab computing environment.
DAQ Data AcQuisition system
Direct counters (D) CED and FPD yields or asymmetries raw
DMCH16X Discriminator Meantimer time digital Converter Histogramming 16 channels vXi, in other words, the French electronics (tdc+)
DNL FORWARD:Differential Non-Linearity: unfortunate fact that each bin in the tdc spectrum is a different width (in time), and that width is a function of time. And we don't know the function, so we have to measure the bin widths regularly with "grey" noise.
DSP Digital Signal Processing
empty target Target is in the "in-beam" position, the beam is hitting the target windows, but the LH2 has been replaced with H2 gas at around 30K.
Energy modulation Maps the detector sensitivity to changes in the beam energy. Not sure how this is actually done….
EPICS Experimental Physics and Industrial Control System software.
EPLD Erasable Programmable Logic Device
ESAD Experiment Safety Assessment Document
ESR End Station Refrigerator: supplies the Halls with 4K and 15K helium coolant for magnets and targets.
Event Transfer buffer
fast feedback  
flyswatter A 30mil thick Al target we could insert just downstream of the H2 cell. It's broken now.
FOPT Studies Chao has been doing to optimize the adiabatic damping factor. An emmittance measuring tool (involves harp scans).
frame target Using the 3.2mm thick aluminum frame of the dummy target holder as a target.
French spikes FORWARD:Feature that occasionally show up in the TOF spectra for the French electronics.  Characterized by one or more tall, narrow (one channel wide) peaks in one or more TOF spectra.  Stopping the run and restarting it appears to cure the problem.
FSD Fast ShutDown. Shuts down beam in less than 5us to all 3 halls if set. It's an OR of many inputs like target motion, ion chamber thresholds, etc.
Genex French white noise box for DNL.  Only one DMCH can be measured at a time.  Slower than using the green blocks for this purpose.
GMS Gain Monitoring System: a laser or flashlamp driven system of optical fibers that can deliver light pulses to the light guides of the G0 detectors for calibration purposes.
G0 Analysis Tool
GUI Graphical User Interface. The silly things on our computer screens we click on and work with.
halo monitor/target A frame with 2 holes (6 & 11mm diameter) on a harp mechanism on the short (new) girder just upstream of the G0 (long) girder. Used to make an absolute measurement of the beam halo.
happyreaper Program that copies our data to the silo.
Harp scan/swipe Moving a set of (usually 3) wires across the beam to measure the beam position and profile.
Herbert's paddle Refers to a scintillation counter paddle sitting on the ferris wheel platform. This guy is just a simple, hard to break or mis-interpret measure of rate in the vicinity of the detectors from beam-tgt interactions. Presently registers about 3uA of anode current (shown on the counting room TV) for 40 uA of beam on LH2.
IA Intensity Attenuator: device/cell in the injector to affect our charge asymmetry: the difference in beam current between helicity states. It changes the intensity of laser light that hits the photocathode.
IA cell Injector suite of devices to affect the IA at 30 Hz. Components are an upstream & downstream linear polarizer, lambda/4 or lambda/10 waveplate, Pockels cell, attenuator.
IA scan To calibrate the IA cell  so that the feedback system can effectively reduce the charge asymmetry. So like changing the intensity deliberately and measuring the helicity correlated charge asymmetry with our BPM.
IHWP Insertable half-wave plate: used to purposefully flip the polarization of the beam, usually on a time scale of a day or two.
Injector Just a placeholder for the link to the songsheets.
IOC Input Output Controller: a computer on a card that talks to our equipment.
Ion Chambers Used to protect our equipment from excessive radiation due to, eg, a steering problem.
LCW Low Conductivity Water: deionized water used for cooling at the lab.
leakage see bleedthrough above.
LEM Linac energy management software system to set RF gradients.
lock Usually applies to the situation where a magnet's current is locked to a certain value. If the current is changed, like to better center our beam, the lock will pull it back to where it was over a time of ~10 seconds or so.
LTD Latching Time Digitizer: the North American tdcs.
MCC Machine Control Center, phone x7046 or 7047. Crew chief is 7045.
MEDM Motif Editor Display Manager software used to look at EPICS stuff. Our main MEDM interface to the accelerator is through Monticello.
MH Counters for the case where in time more than 1 CED and 1 FPD are fired
MH12 Counters of the French electronics for the case where in time either 1 CED and 2 FPD (of one octant) have fired (also for 2 CED and 1 FPD)
MH22 Counters of the French electronics for the case where in time 2 CED and 2 FPD (of one octant) have fired
Moeller The Hall C polarimeter, measures electron-electron scattering from an iron foil with saturated  polarization in a solenoid field.
MPS Machine Protection System: includes FSD, BLM, etc. systems.
MPS Macropulse: Time (~1/30s) during which helicity state is constant.
Munger box A goofy way of saying a splitter. Try signal distribution.
Musson box FORWARD:The YO is essentially the TDC start signal, but fine-tuned (using the Musson box) to reflect the true arrival time of the electron bunch in the hall, just before the target, independent of path length (etc.) through the machine.
NPN Next Pulse Neutralization
NCD Non Conditioned Direct Counter : Yields and asymmetries of the CED or the FPD in time with the trigger signal (OR(CED) AND OR(FPD))
Operational restrictions Beam current limits for different targets, conditions, etc.
OSP Operating Safety Procedure. Also have Temporary ones (TOSP).
OTR Optical Transition Radiation viewer, lets you see the light emitted as the particles go from vacuum into a foil.
PD Program Deputy: MCCs liaison to us and our RC. The PD cell phone number is: 876-7997.
PID Proportional Integral Differential: a feedback or control scheme in common use here at JLab. P for step size response. I for steady state error. D controls settling time/stability.
Pita voltages Voltage applied to the Pockel's cell to adjust the circular polarization of the laser. Affects the beam polarization too of course.
PLC Programmable Logic Controller: a computer & IO device that talks to hardware.
PMT Photo-multiplier tube.
pulsed beam Also called tune beam. 1.525% duty factor. 250us on, 100us off, 4.2us on, all this repeated at 60 Hz. DF=254.2us*60Hz. Note 254.2us=1 macropulse. Note 1 micropulse < 2ps.
PZT Piezo-electric transducer. A mirror whose angle can be changed by application of a voltage at 30 Hz in order to try and null out helicity correlated position differences at our target to the nm level.
PZT scan To calibrate the PZT mirror so that the feedback system can effectively reduce the position differences. So by varying the voltage applied to the mirror, we measure the helicity correlated position differences with our BPMs.
QE Quantum efficiency of the photocathode. Ratio of electrons produced per incident photon.
raster Magnets just at the entrance to the Hall which smear out the beam over the target in order to reduce boiling. G0 uses a square, uniform raster 2mm by 2mm.
RC Run Coordinator: our liaison to MCC, and collaboration focal point for 2 week stints during the expt.
restricted access The hall is in its most accessible state, truck ramp is nominally open. You don't need to contact MCC in order to get in or out.
RF 1497 MHz/3 halls=499 MHz. And 499MHz/16=31.1875 MHz, or 1/(32.064 ns).
RHWP Rotatable half wave plate
RHWP scan Measurements done to find (one of) the RHWP angle(s) that minimizes the charge asymmetry.
RIP scan Doing the suite of 3 things: the RHWP scan, the IA scan, and the PZT scan.
Readout Controller
RWP Radiation Work Permit. Or could be Rotatable Wave Plate.
SEE Switched Electrode Electronics: multiplexing system for BPM readout. Other 2 possibilities are 4-channel, or nanoamp (Hall B) style.
service module The 2' diameter can you see from the outside, that houses the G0 target and its motion mechanism.
Silviu ratio FORWARD: A ratio of asymmetry widths computed 2 ways: By summing the proton peak yield over time bins considered statistically independent, and by considering the proton peak yield as one big bin. Time variation of this ratio is what matters.
SMS The Superconducting Magnet System, ie the G0 magnet.
sniper A PMT HV protection system that will kill the PMT HV if the detector rates get too high, if the SMS goes off, etc. Needs resetting by hand in the electronics room (all the way at the end, red panel, chest high).
Song sheet Equipment location drawings. Click here for a nice colored pdf version.
SOP Standard Operating Procedure.
Superharps   Superharps are used to measure the beam size or profile at the specific locations alone the beam line where beam quality can be characterized.
target out Target is physically completely out of the path of the beam.
Trigger Supervisor
VESDA Very Early Smoke Detection Apparatus.
viewer A BeO plate or OTR foil for viewing the beam shape. Qualitative.
VME Virtual Machine Extension electronics hardware standard.
VXI Vme eXtensions for Instrumentation standard.
Wells plot Plot of measured detector asymmetries as a function of (deliberately varied) charge asymmetry, to characterize the detector sensitivity to the IA.
Wien filter Rotates longitudinal polarization component without affecting position.
WNFM White Noise Fanout Module
YO The YO is essentially the TDC start signal, but fine-tuned (using the Musson box) to reflect the true arrival time of the electron bunch in the hall, just before the target, independent of path length (etc.) through the machine.